class_docstr: Defines the interface for metrics.
code: def log(self):
      tag = common.join_scope(self.prefix, self.name)
      logging.info("%s", "{0} = {1}".format(tag, self.result()))
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import abc
  from typing import Any, Optional, Sequence, Text, Union
  from absl import logging
  import numpy
  import six
  import tensorflow
  from tf_agents.metrics import tf_metric
  from tf_agents.trajectories import trajectory
  from tf_agents.typing import types
  from tf_agents.utils import common
label_desc: Use image node_id 5 for calling the PyMetric obj's underlying member method code with example usage: obj.log() without return types